Early larval frame generation is required when ACC_STRICT_INIT is present, according to the Strict Field Initialization JEP. Since this JEP is preview, we should make strict fields and early larval frame generation be enabled or disabled together by the preview settings, instead of controlling through a hidden flag.

Javac also has a system of proxy locals for code before super. This system is not in conflict with early larval frames, because it transforms code that early larval frames may be entirely omitted. In practice, early larval is only generated when proxy locals are off.